Plasma Antidiuretic Hormone Levels in Cardiac Surgical Patients during Morphine and Halothane Anesthesia

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Abstract
The effects of halothane and morphine anesthesia on plasma antidiuretic hormone (ADH) levels and urinary flow were determined in 18 patients undergoing elective open-heart operations. Patients were divided into 3 groups of 6 each: group I, halothane, 0.5%; group II, morphine, 1 mg/kg; group III, morphine, 2 mg/kg. All patients received N2O O2, 50% each. Measurements of mean blood pressure; heart rate; urinary flow, osmolality and electrolytes; and plasma ADH (by radioimmunoassay) were made prior to induction of anesthesia, 15 and 30 min after induction and 15 and 30 min after surgical incision. Control values for ADH were comparable in all groups (about 3 pg/ml). There was no significant change in any group after induction of anesthesia. After surgical incision ADH levels increased significantly in group I (102 .+-. 29 pg/ml), and group II (42.6 .+-. 25 pg/ml), but not in group III (14.5 .+-. 7 pg/ml). The increase of plasma ADH was significantly higher in group I than in group II or III. Variations in urinary flow were not significant throughout the study. Neither morphine nor light halothane anesthesia stimulated high levels of ADH secretion. The increase in ADH with surgical stimulation was a stress response that can be attenuated by deeper morphine anesthesia. The ADH levels were beyond the physiologic range for antidiuretic action on the kidney, and may represent a vasopressor response. Variations in urinary flow were not ADH-related.